In computer science, an algorithm is a set of steps for a computer program to accomplish a task. Algorithms put the science in computer science. And finding good algorithms and knowing when to apply them will allow you to write interesting and important programs.

Let's talk about a few famous algorithms. How does Google Hangouts transmit live video across the Internet so quickly? They use audio and video compression algorithms.

How does Google Maps figure out how to get from Dallas, Texas to Orlando, Florida so that you can get to Disney World? They use a route finding algorithm.

How does Nasa choose how to arrange the solar panels on the International Space Station and when to rearrange them? They use an optimization and a scheduling algorithm.

For example, let's say that you're writing a game and you want the user to be able to play against the computer. Well, you could look at checkers games for inspiration. Computer scientists have figured out how to write checkers programs that never lose by using the minimax search algorithm to search through the huge tree of possible moves. If your game is similar to checkers, then you might be able to use algorithms based on these techniques. If not, then knowing the limitations of those algorithms might lead you to redesign your game if it requires having a skilled computer player.

1.2 A guessing game

Let's play a little game to give you an idea of how different algorithms for the same problem can have wildly different efficiencies. The computer is going to randomly select an integer from 1 to 16. You'll keep guessing numbers until you find the computer's number, and the computer will tell you each time if your guess was too high or too low:

Maybe you guessed 1, then 2, then 3, then 4, and so on, until you guessed the right number. We call this approach linear search, because you guess all the numbers as if they were lined up in a row. It would work. But what is the highest number of guesses you could need?